A Wisconsin man recently became the latest alleged sex abuse victim to sue Pope Benedict XVI and the Vatican. But the Vatican is a sovereign nation, and — as its head of state — the pope is often considered immune from such suits under international law. Is it possible to sue the Pontiff? Here's a quick guide:

What's the Wisconsin case about?The Wisconsin plaintiff, identified as "John Doe 16," says Pope Benedict and other senior Vatican officials failed to discipline Rev. Lawrence Murphy who allegedly molested up to 200 boys at a school for the deaf from 1950 to 1974 before his 1998 death. (Watch a BBC report about the claim.) The plaintiff's attorney, Jeff Anderson, is arguing that the Vatican is essentially a global business empire, with the pope as CEO — liable for what goes on in individual dioceses, due to its "commercial activity" (i.e. fundraising) there.

What are John Doe 16's chances of success?Many legal experts say the lawyer's argument won't stand up in court. To date, individual dioceses have typically been treated as independent entities. But Anderson also hopes the lawsuit will force the Vatican to turn over "secret" documents on other accused priests.

Does pope Benedict have an American lawyer?Yes. Jeffrey Lena, a Berkeley, CA-based attorney who specializes in sovereign immunity, has become "the pope's de facto spokesman" in America. Lena first helped the Vatican when one of its banks was accused of holding valuables stolen by Nazi sympathizers.

Are there other suits against the pope?Several, though none has been successful — yet. So far, legal judgments on the matter have been contractory.

How so?In 2005, a federal judge in a Texas sex-abuse case ruled that the pope is immune from prosecution as the sovereign leader of Vatican City. Not so fast, said the 9th Circuit Court of Appeals more recently. If lawyers can prove that the offending priest is a direct employee of the pope, the Vatican may be vulnerable. Since the United Nations doesn't officially recognize Vatican City as a state, some lawyers make the long-shotargument that the pope lacks soverign immunity.

If he can't be sued, can the pope be arrested?Two British athiests hope to do just that, but actual arrests of heads of state are rare: Panama's Manuel Noriega and Yugoslavia's Slobodan Milosevic are exceptions.